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Understanding AC phase relationship...

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It is hard to get you what you seem to want because words are not sufficient to describe the situation. A picture, or a drawing, or a schematic might be helpful. One of the hard things to quantify is the strength of the magnetic field, how the field is changing, and how efficient the coupling is to your coil.

A simulator may or may not be helpful in describing and understanding the situation. Now a coil that is shorted is similar to a small resistor in parallel with an inductor. If that is what you are talking about I'm thinking that it will be mostly uninteresting.

BTW with a small resistance (10 milliohms) across the coil the output voltage and current are quite small but they are still out of phase. This is as true at 60 Hz as at 100KHz.
 
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Another point.

I'm not sure why it is so "shocking" to consider that a coil, choke, or transformer in a circuit, at some point in an AC cycle, is seen at the supply as (in essence) a short.

Maybe my ability to describe those conditions is lacking. I'm not an engineer or physics professor. I think in more "animated" or graphic terms.

I also do not follow, precisely, how voltage and current being out of phase equals no power.

Just because they aren't in phase, this doesn't mean they aren't still "there" and calculable, right? I mean if a voltage of y exists in x circuit, and a current of z exists in x circuit, then ohms law still applies (P=ExI), no matter what point in time they occur, correct? Wouldn't this be because in AC, we talk of AVERAGE current and AVERAGE voltage, not peak...right?

Maybe I'm missing something, but I am here to learn.

I think of a dead short, which in actuality is never a perfect short as all conductors have resistance...but this is true whether AC or DC....As minimal as the resistance is, when the current has spiked and all those electrons are bursting through the seams to get through, if I measured the voltage across the short with a meter, would it not be close to zero and out of phase with the current? Yet, nobody can argue that there is no power there. There might even be a small fire!

Voltage is potential, or electrical pressure...and when there is a short, it is no longer potential but rather an occurance whose potential has been released.

I think of a cylinder of compressed air with a pressure gauge and a valve. I open the valve a little, there is flow. There is still some potential because there is resistance in the valve. As I open it, that potential is exchanged for increased flow. The pressure drops a bit at the gauge. If my valve had a large enough oriface to create a large enough flow, I might see the needle on the gauge drop to near zero lbs of pressure, depending on what the supply pressure was to begin with.

Maybe I think in too simple terms for this hobby :p
I think you're on solid ground, and I do have advanced degrees in engineering. Sorry about the QRT situation.
 
OK to be honest since this seems complex. I have a secondary coil only to consider. it is in direct short. The magnetic field from the primary is generating the voltage and thus amperage in the secondary. I don't reall care or am concerned with the voltage or amperage phase of the primary. All I'm concerned about is the voltage and amperage phase of the secondary. So its really just voltage to amperage thru the secondary coil to consider. Does this help. And I need a formula cause I'm building software to chart the data. I can't use online calculators really since they don't plug into the program. I need formulas. And thanks for your guys help, I'm a little confused at this point.

How is the amperage affected? Isn't it limited by the inductive reactance only?

The pdf I linked to at some point has the formulas for calculating all of that. And if you followed the discussion, (in which I'm learning and thinking through things myself), then you might have picked up that these phase voltage, current, power, and reactance values are frequency dependant. I myself had never really considered them at line frequencies, and the light bulb went on when that was mentioned.

I understand your confusion and I apologize if I haven't helped.
If that pdf doesn't suffice, I hope someone else will chime in with better info.
 
I think you're on solid ground, and I do have advanced degrees in engineering. Sorry about the QRT situation.

Ah, you looked up my callsign on QRZ :)

Well, I got remarried and had a baby in the past couple of years and decided to put the equipment in storage to make room for more important things. In a few years I'll be getting a bigger house with a room just for my radios.
 
Here is a transformer simulation in case anybody is interested. Do eiter the transient analysis or the AC analysis.
 

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Ah, you looked up my callsign on QRZ :)

Well, I got remarried and had a baby in the past couple of years and decided to put the equipment in storage to make room for more important things. In a few years I'll be getting a bigger house with a room just for my radios.
Well maybe congratulations are in order then. '73 and Nice to meet you
 
It is hard to get you what you seem to want because words are not sufficient to describe the situation. A picture, or a drawing, or a schematic might be helpful. One of the hard things to quantify is the strength of the magnetic field, how the field is changing, and how efficient the coupling is to your coil.

A simulator may or may not be helpful in describing and understanding the situation. Now a coil that is shorted is similar to a small resistor in parallel with an inductor. If that is what you are talking about I'm thinking that it will be mostly uninteresting.

BTW with a small resistance (10 milliohms) across the coil the output voltage and current are quite small but they are still out of phase. This is as true at 60 Hz as at 100KHz.


First of all PabaBravo, I should have realized those must be initials in phonetics :) Are you an active ham? Thanks for congrats and 73s to you as well.

I miss CW BTW, I'm a big proponent of pounding brass.

Just wanted to mention something to the original poster, while I'm enjoying some nice conversation (wife and baby are sleeping).

The last comment that PB made is key. What he is saying, as far as line frequencies go, is that if a purely resistive load of significant value is placed on your secondary, the impedance of the tranformer being so negligeable at that frequency, the resistive element will dominate the circuit. Purely resistive circuits are in phase. As voltage increases, so does current. Your transformer/resistor circuit is not purely resistive, at line frequencies, but transformer reactance is so negligeable in this case that it might as well be purely resistive.

Think about my compressed air. If I am running a compressor to increase the pressure, and have my valve cracked open but at a STEADY resistance, as the pressure increases so will the flow out of my valve. Pressure and flow in this case are in phase, because the unchanging variable is the resistance.

But, as he said, if I have a resistance that is small as to be a near short, no matter what frequency we are discussing, the phase shift will occur, as I described earlier with the other compressed air analogy, ie gauge pressure drops and flow skyrockets when my valve is wide open.

The concept of "phase" sounds way more mysterious than it is. It is all about the 3-fold interractions of voltage,current, and resistance, and ohms law.
 
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I also do not follow, precisely, how voltage and current being out of phase equals no power.
In an AC circuit there is real power and reactive power. Real power (which transmits actual power) is from the component of current that is in phase with the voltage. Reactive power (which transmits no power) is the current component that is 90 degrees out of phase with the voltage. The real power equals the RMS voltage times the RMS current times the cosine of the phase angle between the voltage and current.

A phase angle of 90 degrees occurs when driving a pure inductive or pure capacitive load. A pure inductor or capacitor dissipates no real power, only reactive power. You can thus see how you can have current and voltage with no real power.

The power company quantifies the value of real power with Power Factor. The Power Factor varies between 1, when the current is in phase with the voltage, to 0, when the current is 90 degrees out of phase with the voltage. Power companies obviously want to keep the PF as close to one as possible, to minimize useless reactive currents flowing in the power lines.
 
I have worked with transformers. I have measured them and simulated them and I'm here to tell you that the current and voltage on the secondary of a transformer are most definitely not in phase with each other at least as far as I understand the meaning of that term.

One of them may be in phase with the alternating magnetic field that generated the output on the coil. It is also the case that the output of a generator does not have the current and voltage in phase with each other. If it was possible to get a generator to do that, the whole power factor correction industry would be a solution looking for a problem.

You can continue to insist on any particular fantasy that you like, but you should be mindful of the damage you are doing to people trying to learn.
Fantasy? That's getting a little nasty. Advanced degree(s) in engineering don't necessarily make you right (although you apparently think it allows you to disparage other's comments).

You seem to be somewhat mixing cause and effect. Perhaps the problem is, you are apparently talking about high frequency circuits which have a lot of inherent capacitance and inductance in their load, which affect the transformer operation, and I'm talking about low frequency circuits (such as a power line). For such a transformer the current and voltage are in phase for a resistive load. It's the same for a generator. Of course if you add a significantly reactive load then the voltage and current are no longer in phase, which is where power factor correction comes into play. But that's a function of the load, not the transformer or generator.

Thus for a transformer or generator, the real power output is that portion of the current and voltage that is in phase. Any portion out of phase is reactive or imaginary power. This applies to power at any frequency.

That's not fantasy.
 
In an AC circuit there is real power and reactive power. Real power (which transmits actual power) is from the component of current that is in phase with the voltage. Reactive power (which transmits no power) is the current component that is 90 degrees out of phase with the voltage. The real power equals the RMS voltage times the RMS current times the cosine of the phase angle between the voltage and current.

A phase angle of 90 degrees occurs when driving a pure inductive or pure capacitive load. A pure inductor or capacitor dissipates no real power, only reactive power. You can thus see how you can have current and voltage with no real power.

The power company quantifies the value of real power with Power Factor. The Power Factor varies between 1, when the current is in phase with the voltage, to 0, when the current is 90 degrees out of phase with the voltage. Power companies obviously want to keep the PF as close to one as possible, to minimize useless reactive currents flowing in the power lines.

I see the conversation is still active, which is a good thing if it sheds light for the OP who started the thread.

Before I reply to your comment, it is with a heavy heart that I just this morning discovered one of my heroes has passed away. I have been inactive in my radio hobby for a couple of years now and have not done much reading on antennas and radio theory. A brilliant man, LB Cebik (W4RNL), an amateur radio guru who was anything but an amateur, went "silent key" last year. In doing some refresher reading I went to his website only to see he had passed away and that a commercial entity had taken his site over. At least it has free registration and hasn't become a pay site! Cebik freely passed along his knowledge and I would hate to see someone else profit from his legacy.

At any rate, you bring up real vs reactive power, and in fact you are correct that these two variables coexist in AC theory. But in backpeddling from your original thesis you further muddy the waters for the original OP, methinks. I do not know the OPs knowledge base, but assuming he is just starting to learn AC theory I think it is important to focus on the THEORY which encompasses quite a bit of applications, not limited to "power distribution" and power supply transformers.

You bring up real vs reactive and seem to imply that "real power" is some way more desireable than reactive power, or more "real", LOL, which is a deceptive word. If all electronic circuits were designed to energize light bulbs, turn a motor, etc, then you might have a point. However, this is not the case thankfully or my cellphone and radio equipment wouldn't work.

In radio, in fact, REACTIVE power is the desireable power and "real power" is what we seek to mitigate.

If the OP or anyone cares to register on Cebik's webiste, you can access the following URL:

https://www.cebik.com/content/a10/tales/name.html

Which talks in an introductory way about various antenna types. But no matter the design, antennas work on the same principle which is a demonstration of a nearly pure reactive element in an AC circuit, and in function behaves much like a tranformer at radio frequencies...except instead of inducing a current into another coil, the antenna induces radio waves into the surrounding environment.

It seems magical that a radio transmitting hundreds or thousands of watts of power into an antenna and transmission line system has little "visible" evidence of the power. We are used to seeing power at work in the form of mechanical movement, light, heat, etc. Well, no antenna is perfect and some RESISTIVE impedance occurs, causing SOME heat. However, if it is efficient we hope that the majority of the power makes its way into the ether as radio waves.

And that power IS demonstrable. We CAN see how significant it is. My QRP (5 watt or less) radios are capable of sending a signal hundreds, thousands of miles, to be received by another antenna (which behaves the same way in reverse when in RX mode) This is reactive power at work, desireable, predictable, measureable, and perfectly relevant to AC theory.

Again, the effects of "real power" in radio are to create heat in exchange for radio energy, which is an undesireable biproduct.

If you scroll down on this W4RNL webpage at the bottom, you will see a modelled depiction of the current and voltage distribution of a half wave "dipole" as well as "doublets". In the case of the dipole, at resonant frequency we have current and voltage distribution as such that along the length of the dipole from one element to the other, there is one half cycle of AC, with the instance of maximum current 90 degrees out of phase with maximum voltage, the peak voltage measured at the two ends of the dipole and current distributed along its length, maximum at the feedpoint.

The doublet is an antenna working at multiple wavelengths, with multiple points of peak current and peak voltage along its length. In amateur radio our "bands" are arranged somewhat optimally so that they are multiple wavelengths of each other, so doublets can be used as multi-band antennas. Optimally, the doublet working on a fequency which is a multiple of its resonant frequency (ie 160 meter dipole operating at 40 meters) the voltage and current peaks will still be evenly distributed along the elements, with the ends still being instances of peak voltage...only in this case the feedpoint may or may not be an instance of peak current or peak voltage.

Now, I realize I went into great detail about antennas and not coils and transformers, but the point is that AC theory has fundamentals that are applicable and critical for thorough understanding. Getting bogged down with 60 hz power distribution muddies the discussion. Unless the OP is only interested in becoming an electrician or engineer at a power plant, he needs to understand more than "real power" and should consider the applications of "reactive power".
 
I'm not sure that post helped the OP either. He just wants to know how to measure the power-factor out of a coil being induced by a magnetic field.

dev, easiest would be to measure the peaks of both current and voltage, then calculate how much time they are out of sink.

if time == 0 then they are in phase == 1.0 PF
if time == 1/4 freq period then they are 90degrees out of phase == 0.0 PF.
Just interpolate the rest based on the wave form.
 
I'm not sure that post helped the OP either. He just wants to know how to measure the power-factor out of a coil being induced by a magnetic field.

dev, easiest would be to measure the peaks of both current and voltage, then calculate how much time they are out of sink.

if time == 0 then they are in phase == 1.0 PF
if time == 1/4 freq period then they are 90degrees out of phase == 0.0 PF.
Just interpolate the rest based on the wave form.
As I read the original question it was not about measurement, but a theoretical query about weather in an inductor with some parallel resistance is it possible to have the current and voltage in phase giving a power factor of 1. My answer is that it is not. We have a difference of opinion which can be settled by either a coherent theoretical proof or by experiment. However, even in the face of overwhelming evidence some people will remain unconvinced. This appears to be such a case, and thus it is pointless to continue this thread.
 
smanches,

I currently can't measure the peaks as I have no oscilliscope at the moment. I will buy one eventually, but for now I'm out of luck, I can only calculate. And that is what I must do I guess. Although I would love to get my hands on an oscilliscope, I think I soon will.

I'm really interested in formulas for calculating phase, I'll look at the PDF now and see if I can use something in there.

Guys, I calculated the inductive reactance earlier and used it to calculate the amperage at different points, is that the correct way to do it? I got in phase amperage and voltage, which makes me think its incorrect since I calculated it at 6khz which everyone seems to agree is out of phase.
 
ke5frf,

I got into the PDF and noticed that I can get the phase angle from the reactive inductance of the coil. Basically theta equals the arctan of the reactive inductance.

So my question is this: does my value for the reactive inductance change at different points along the voltage wave, or is it a constant value throughout the wave?

I think that may be the answer I'm looking for. Thanks.
 
devronious,

Glad the pdf helped...I didn't write it, just Googled it.

There is a point with all the math and trigonometry where my brain starts turning to mush and the concepts begin to confuse me. Probably why I'm not an engineer.

So I will defer explaining the math to someone more qualified.

And I certainly HOPE that some of the things I mentioned helped reinforce your understanding of the theory. In fact, I would appreciate feedback about that. The Cebik webiste I linked to, if you are so inclined, will open your eyes in a lot of ways. If you get time I highly encourage some reading.

Good luck with digging into all the math and modelling this with software.
 
You bring up real vs reactive and seem to imply that "real power" is some way more desireable than reactive power, or more "real", LOL, which is a deceptive word. If all electronic circuits were designed to energize light bulbs, turn a motor, etc, then you might have a point. However, this is not the case thankfully or my cellphone and radio equipment wouldn't work.

In radio, in fact, REACTIVE power is the desireable power and "real power" is what we seek to mitigate.
.
Real power is real power, independent of the application or frequency. You seem to be confusing reactive power with the radiated power from an antenna. Real power is the power that goes out the antenna and is indeed the desirable power. If you have an antenna perfectly matched to the transmission line characteristic impedance driving it, then it will look like a resistance (i.e. the RF current is in phase with the voltage), there is no reactive power, and all the real power is radiated. That is the whole point of tuning the antenna to match the transmission line and minimizing SWR. You only get reactive power if the antenna is mismatched. Reactive power does no work and is generally undesirable.

The phrase "reactive power' is somewhat of a misnomer since there is no power involved in the normal sense of the term. It is more accurately called imaginary power since it can have a value of volts times amps, but it does no work.
 
As I read the original question it was not about measurement, but a theoretical query about weather in an inductor with some parallel resistance is it possible to have the current and voltage in phase giving a power factor of 1. My answer is that it is not. We have a difference of opinion which can be settled by either a coherent theoretical proof or by experiment. However, even in the face of overwhelming evidence some people will remain unconvinced. This appears to be such a case, and thus it is pointless to continue this thread.

Although he said when being induced by a magnetic field. This is the difference that makes it have a PF of 1.
 
OK, I am comfortable with being incorrect with some terms and some concepts. I do not wish to contribute to any confusion. It has, admittedly, been a while since I studied or applied much of this stuff, and...use it or lose it so to speak.

I do feel like I've mixed up a thing or two in my own mind so I'm going to dig out some books and read.
 
I'm digging into it all right now too. There is almost no information about the phase relationship on the output windings of transformers.

I'm just going to have to setup the experiment at home tonight, since simulation does not seem to satisfy everyone.
 
OK, perhaps this is where I am wrong or misunderstand...Or perhaps I am right or half-right. Whatever.

RADIATION OF ELECTROMAGNETIC ENERGY

I know this thread is about coils and transformers, but it has always been my understanding that AC theory is the same "forest" despite differences in the "trees", so that is why I keep going back to RF transmission and antennas.

On the page I linked, it states this:

4-6 1. A current flows in the antenna with an amplitude that varies with the generator voltage. 2. A sinusoidal distribution of charge exists on the antenna. Every 1/2 cycle, the charges reverse polarity. 3. The sinusoidal variation in charge magnitude lags the sinusoidal variation in current by 1/4 cycle.

A 1/4 cycle is 90 degrees out of phase.

At the top of the page, if you click "previous page", (not the windows icon, but rather the link provided on the page) you see the same depiction from the Cebik site showing current and voltage distribution, 90 degrees out of phase.

I have always concluded that in a properly tuned antenna system that voltage and current where not in phase.

Yet in doing a little reading of other webpages I'm getting some contradictions.
So it definately looks like reading an actual BOOK instead of the internet, to refresh, is in order LOL.
 
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